The present invention relates to a transfer ribbon cassette and particularly to a cassette having mounted therein a pair of ribbon rolls having an improved ribbon winding pattern from one ribbon roll to the other.
A conventional transfer ribbon cassette in a line printer is seldom reused, after the ribbon has been completely wound from the reel on the ribbon pay-out part to the reel on the ribbon take-up part, for such purpose, for example, as to utilize any remaining ink on the ribbon. If it is possible to reverse the front and back surfaces of the cassette corresponding to opposite sides of the ribbon rolls, the ribbon is rewound, with the former ribbon take-up part now becoming the pay-out part, the take-up reel being driven in the same direction of rotation as in the initial load of the cassette. In the case where a cassette receptacle means does not allow one to reverse the cassette surfaces, it may be preferable to invert the cassette by turning it in the plane of rotation of the ribbon rolls, or ribbon winding (or rewinding), through 180.degree..
However, in the conventional ribbon cassette, when such a plane inversion of the cassette has been made for rewinding operation, the reel which becomes the take-up reel must be driven in the opposite direction of rotation from the direction of rotation of the original take-up reel in the original load of the cassette. It should be noted that with the conventional ribbon cassette a cassette receiving arrangement is provided having a driving gear engaged with a gear of the reel as the take-up part, the cassette receiving arrangement having a brake mechanism and a back-tension mechanism to be associated with the other reel, so that the cassette receiving arrangement will be more complicated for a plane inversion rewinding operation. In addition, the arrangement will be much more complicated for a normally rewinding operation without any inversion of the cassette.
Nevertheless, it is considered that plane inversion of a ribbon cassette and the rewinding operation as described above is advantageous to address the relation between printing defects on a printed sheet and the surface exhibition of the ink ribbon.
In the ribbon cassette in general use, the ribbon has an ink layer on only one surface, as described above. Recently, a ribbon having ink layers on both surfaces is being developed. In such ink ribbon, it is convenient to devise an arrangement such that when one ribbon surface has been used, with the ribbon completely wound from one reel to the other, the cassette is reset by inverting itself through 180.degree. in the ribbon winding direction or in the plane of rotation of ribbon rolls to use the ink layer on the opposite surface.
In such cassette resetting system based on plane inverting, the duration of use of the same cassette tends to be long, and the cleaning or inspection of the head or the reverse setting of the cassette results in the frequent slacking of the ribbon; thus, it is desired to make it possible for the user to rewind the ribbon to remove the slack in a simple and reliable manner without putting his hands on the ribbon. The reason is that if he puts his hand on the ribbon, the ribbon tends to wrinkle along its width and thereby degrades the printing quality.
Accordingly, it is a primary object of the present invention to provide a novel transfer ribbon cassette capable of a rewinding operation by driving a reel positioned at take-up side in the same direction of rotation with that of the original take-up reel, when the cassette is inverted in the plane of rotation of ribbon rolls.
It is another object of the present invention to provide a novel ribbon cassette having a two-surface type ink ribbon mounted therein, with the transfer ribbon cassette having a mechanism allowing the user to remove slack in the ribbon simply and reliably.